This is a study of the sustainability of Brazilian ethanol and the socio-environmental aspects of production methods and processes used in the sugar and alcohol sector and of the substitution of gasoline with ethanol fuel. The study also presents opportunities for expansion of the international market for this product that have appeared with the growing search for substitutes for fossil fuels, which are bound to run out and which are responsible for a large part of the emission of CO2 into the atmosphere. These opportunities are substanciated by the objectives laid down in the Kyoto Protocol, which stipulate the reduction in the emission of greenhouse gasses, favoring investment in renewable energy sources, less poluting technologies and sustainable development. In Brazil, which was a pioneer in the development of alcohol fuel in large scale and which is currently the largest exporter, there are large areas which can be used to expand production and make the country the market leader. This is the view of the country s government, which has made diplomatic efforts to promote ethanol as a leading Brazilian export commodity, including negotiations with the WTO to gain better access to the market. However, the aspects assessed in this study are a warning of the socio-environmental impact associated with this expansion.